Green water in established tank - again!

[jfwilson54]

I've had green water now for the third time this summer in my heavily planted, well-established tank. 3-day blackout gets rid of it, but it comes back in 2-3 weeks. Any ideas? I probably have excess organics due to overpopulation and should reduce the fish count a bit.

Here's the setup:

29 gallon. 2 x T-5 double bulbs (4 x 18 watts - medium light)
lights on about 10 hrs/day
CO2 injection DIY yeast method, CO2 ranges from 8 to 18 usually
Many happy plants
weekly 25% water change/gravel vac/plant pruning, 1/2 cap Flourish
PH range 6.7-7.1, KH 45-70, No2 is 0, Phosphate about 1

Fish:
pleco; 2 cory cats; 1 Kuhli loach
4 big snails (1.5 inch)
3 small ottos
1 Chinese algae eater, 1 Siamese, both big now
1 betta
2 silver tetras, 4 neon tetras
2 platys
2 glass cats

I'd appreciate any ideas. Before first blackout, I tried various treatments, although I have not tried "Algone".